/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_sparse_f32.c
*
* Description:	Floating-point sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* ------------------------------------------------------------------- */
#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters
 *
 * This group of functions implements sparse FIR filters.
 * Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero.
 * Sparse filters are used for simulating reflections in communications and audio applications.
 *
 * There are separate functions for Q7, Q15, Q31, and floating-point data types.
 * The functions operate on blocks  of input and output data and each call to the function processes
 * <code>blockSize</code> samples through the filter.  <code>pSrc</code> and
 * <code>pDst</code> points to input and output arrays respectively containing <code>blockSize</code> values.
 *
 * \par Algorithm:
 * The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients.
 * This is in addition to the coefficient array <code>b</code>.
 * The implementation essentially skips the multiplications by zero and leads to an efficient realization.
 * <pre>
 *     y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] * x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]]
 * </pre>
 * \par
 * \image html FIRSparse.gif "Sparse FIR filter.  b[n] represents the filter coefficients"
 * \par
 * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>;
 * <code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>;
 * <code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where
 * <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array.
 * Some of the processing functions also require temporary working buffers.
 *
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient and offset arrays may be shared among several instances while state variable arrays cannot be shared.
 * There are separate instance structure declarations for each of the 4 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * Set the values in the state buffer to zeros before static initialization.
 * The code below statically initializes each of the 4 different data type filter instance structures
 * <pre>
 *arm_fir_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q7 S =  {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 * </pre>
 * \par
 *
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the sparse FIR filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Sparse
 * @{
 */

/**
 * @brief Processing function for the floating-point sparse FIR filter.
 * @param[in]  *S          points to an instance of the floating-point sparse FIR structure.
 * @param[in]  *pSrc       points to the block of input data.
 * @param[out] *pDst       points to the block of output data
 * @param[in]  *pScratchIn points to a temporary buffer of size blockSize.
 * @param[in]  blockSize   number of input samples to process per call.
 * @return none.
 */

void arm_fir_sparse_f32(
    arm_fir_sparse_instance_f32* S,
    float32_t* pSrc,
    float32_t* pDst,
    float32_t* pScratchIn,
    uint32_t blockSize)
{

	float32_t* pState = S->pState;                 /* State pointer */
	float32_t* pCoeffs = S->pCoeffs;               /* Coefficient pointer */
	float32_t* px;                                 /* Scratch buffer pointer */
	float32_t* py = pState;                        /* Temporary pointers for state buffer */
	float32_t* pb = pScratchIn;                    /* Temporary pointers for scratch buffer */
	float32_t* pOut;                               /* Destination pointer */
	int32_t* pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
	uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
	uint16_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter  */
	int32_t readIndex;                             /* Read index of the state buffer */
	uint32_t tapCnt, blkCnt;                       /* loop counters */
	float32_t coeff = *pCoeffs++;                  /* Read the first coefficient value */



	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_f32((int32_t*) py, delaySize, &S->stateIndex, 1,
	                      (int32_t*) pSrc, 1, blockSize);


	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
	                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
	                     blockSize);

	/* Working pointer for the scratch buffer */
	px = pb;

	/* Working pointer for destination buffer */
	pOut = pDst;


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	/* Loop over the blockSize. Unroll by a factor of 4.
	 * Compute 4 Multiplications at a time. */
	blkCnt = blockSize >> 2u;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in destination buffer */
		*pOut++ = *px++ * coeff;
		*pOut++ = *px++ * coeff;
		*pOut++ = *px++ * coeff;
		*pOut++ = *px++ * coeff;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	 * compute the remaining samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in destination buffer */
		*pOut++ = *px++ * coeff;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {

		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
		                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
		                     blockSize);

		/* Working pointer for the scratch buffer */
		px = pb;

		/* Working pointer for destination buffer */
		pOut = pDst;

		/* Loop over the blockSize. Unroll by a factor of 4.
		 * Compute 4 MACS at a time. */
		blkCnt = blockSize >> 2u;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pOut++ += *px++ * coeff;
			*pOut++ += *px++ * coeff;
			*pOut++ += *px++ * coeff;
			*pOut++ += *px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* If the blockSize is not a multiple of 4,
		 * compute the remaining samples */
		blkCnt = blockSize % 0x4u;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pOut++ += *px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = ((int32_t) S->stateIndex -
		             (int32_t) blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

#else

	/* Run the below code for Cortex-M0 */

	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* Perform Multiplications and store in destination buffer */
		*pOut++ = *px++ * coeff;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {

		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_f32((int32_t*) py, delaySize, &readIndex, 1,
		                     (int32_t*) pb, (int32_t*) pb, blockSize, 1,
		                     blockSize);

		/* Working pointer for the scratch buffer */
		px = pb;

		/* Working pointer for destination buffer */
		pOut = pDst;

		blkCnt = blockSize;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			*pOut++ += *px++ * coeff;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex =
		    ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

#endif /*   #ifndef ARM_MATH_CM0        */

}

/**
 * @} end of FIR_Sparse group
 */
